Current study analyzes dynamic instability of evaporator tube array at heat recovery steam-generator (HRSG) that encounters repetitive tube vibration failure. The tube array experiences turbulent swirling flue-gas. The analysis according to ASME criteria predicts critical instability velocities at 26.2 m/s, dimensionless reduced velocity factor at 85.7 and dimensionless mass damping at 50.2. These levels create large response of high vibration amplitude of tube reflecting strong coupling between tube structure and exhaust gas. CFD model for exhaust gas flow regime upstream tube array predicts large variation in velocity. The model is not validated but results agree with experience of repetitive tube failure within the high velocity profile sections. The calculated natural frequency of tube is 6 Hz, dimensionless reduced mass damping factor of tube is found at 243 meeting ASME criterion of greater than 64. Thus, synchronous vortex shedding vibration will not occur at the tube. Last, HRSG encounters structural vibration, cracks and high noise level at stack side. Fundamental acoustic frequency and vortex shedding frequency are calculated at 65 Hz and 134 Hz, respectively. These values don’t meet 80–120% range. Thus acoustic vibration noise will not occur.

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